v2.1: Bundle Bird X search - no external CLI needed

Vendor Bird's Twitter GraphQL search client directly into /last30days,
eliminating the dependency on `npm install -g @steipete/bird`. X search
now works out of the box with just Node.js 22+ and browser cookies.

- Add vendored bird-search.mjs wrapper (search-only subset of Bird v0.8.0)
- Vendor @steipete/sweet-cookie for browser cookie extraction
- Update bird_x.py to call vendored Node.js module instead of `bird` binary
- Update README.md and SKILL.md for v2.1 (remove Bird CLI install steps)
- Include Bird's MIT LICENSE in vendor directory

The fallback chain is: vendored search -> xAI API key -> web-only mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SKILL.md

@@ -1,11 +1,12 @@
 ---
 name: last30days
+version: "2.1"
 description: Research a topic from the last 30 days on Reddit + X + Web, become an expert, and write copy-paste-ready prompts for the user's target tool.
 argument-hint: 'nano banana pro prompts, NVIDIA news, best AI video tools'
 allowed-tools: Bash, Read, Write, AskUserQuestion, WebSearch
 ---
 
-# last30days: Research Any Topic from the Last 30 Days
+# last30days v2.1: Research Any Topic from the Last 30 Days
 
 Research ANY topic across Reddit, X, and the web. Surface what people are actually discussing, recommending, and debating right now.
 
@@ -251,7 +252,7 @@ KEY PATTERNS from the research:
 ---
 ✅ All agents reported back!
 ├─ 🟠 Reddit: {N} threads │ {N} upvotes │ {N} comments
-├─ 🔵 X: {N} posts │ {N} likes │ {N} reposts (via Bird/xAI)
+├─ 🔵 X: {N} posts │ {N} likes │ {N} reposts
 ├─ 🌐 Web: {N} pages (supplementary)
 └─ 🗣️ Top voices: @{handle1} ({N} likes), @{handle2} │ r/{sub1}, r/{sub2}
 ---